Benign Transient Hyperphosphatasemia in Adults: Case Report and Literature Review

Benign transient hyperphosphatasemia (BTH) in children is characterized by temporary highly elevated serum alkaline phosphatase (ALP) activity in the absence of liver or bone disease and a return to normal within 3 to 4 months. Since its first description in the 1950s, several cases of BTH in infants and children have been reported. Although there is no known etiology for this illness, it has been associated with viral infections. This condition has rarely been seen in the adult population, and there is scarce available information. The sialylation of the ALP isoenzymes decreases their renal clearance from the circulation; however, the pathophysiology behind the increased sialylation of the ALP is uncertain.

This is a 62-year-old female with a history of hypertension who was seen for a routine checkup and was found to have elevated ALP. The patient reports a family history of primary biliary cirrhosis. Routine labs showed an isolated elevation of ALP at 1496 U/L (normal range is 44 to 147 U/L). A physical examination and review of systems revealed no evidence of liver disease or bone abnormalities. Lipase, thyroid-stimulating hormone (TSH), T3, T4, parathyroid hormone, vitamin D, electrolytes, and markers for autoimmunity and tumors were found within normal limits. The abdominal ultrasound, the computerized tomography (CT) with contrast of the abdomen, and the bone survey were unremarkable. Alkaline phosphatase electrophoresis showed equally elevated liver and bone isoenzymes with a typical pattern of BTH. Serial ALP levels showed normalization by week 8 from the initial abnormal level.

Benign transient hyperphosphatasemia is a rare condition mostly seen in children, and it is even rarer for it to present in adults. It is speculated that BTH is caused by a transient decrease in the clearance of ALP. The adult presentation of BTH is poorly described in medical literature, limiting the ability of medical providers to make an early diagnosis and avoiding extensive investigations.